Electric muffle.



PATENTED MAY 1, m06.

E. ZELL. ELECTRIC MUPPLE.

APPL'IATION 'FILED OCT. Z8, 19021 Inventor. Erlcmd Zell, .bs

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unirnoappa ERLAND ZELL, UF SCHENEUTDY, NEW YRK, ASSIGNUR T GENERAL ELECTRIC COMPANY, A UGRPUBA'HN 0F NlW YORK..

' Specication of Letters Patent.

Patented May l, 12?@8.

l l Application tiled October 28, 1902. Serial No. 129,132.

tain new and useful Improvements in Electric lclufiies, of which the following is a speciiication.

lron forms a very desirable substance from which to construct the walls of inutiles or furnaces which are to be heated. by the pas-` sage of electricity through such walls. When so constructed, however, without provision y being made for protecting the walls of the furnace, they deteriorate rapidly. This deterioration is due principally to the oxidation of the iron, which takes place almost entirely from 'the outer surface inward. rlhis oxidation may be dons away with if the iron be kept in an inclosed space to which no air or other gas-containing oxygen is admitted. The construction, however, of such an inclosing chamber is not simple, owing largely to the diiliculty caused by thexpansion of the lheated iron at any joints which 'may be made. The use of carbon, charcoal, or the like as a packing for the tube to reduce the oxidation has the disadvantage that it cements the iron, and thereby reduces vits melting-point. j

l have found that if the iron` heatingchamberbe packed in or surrounded by some carbid oxidation will not take place nor will the iron be affected by the carbid. The carbid which I prefer to employ is granular calcium carbid. The Slction of the heated` chamber upon the calcium-carbid packing in the presence of any air which may come in through the packing is principally to produce carbon monoxid and calcium oXid. The calcium oXid which is formed has a very high melting-point, and since it is entirely free from moisture adds to the efficiency ofthe combination. The carbon monoXid, owing to its high powers .as a reducing agent, also hel s materially to protect the tube.V 1IWith suc a packing an iron-chamber furnace can be run at a temperature of about 1,1000 centigrade and the life of the chamber is of considerable duration. In the use of my invention it may become necessary to renew the calcium carbid employed rom time to time. The intervals between renewals, however, will. be of considerable duration.

For a better understanding of my invention reference may. be had to the accompanying drawings, in which I have illustrated one embodiment of my invention. An elongated iron tube 1 forms the heating-chamber proper of the furnace. This tube may be a section of iron pipe and is preferably threaded at the ends, as shown. On these threaded ends are'screwed heavy nuts 2 and 3. casing e surrounds the tube l. This casing is shown in the drawings as made of sections oi vitriiied or otherearthenware pipe. Within the casing' a layer-or lining 5 of suitable heat-insulating material, such as lime or asbestos, is placed, and within this heat-insulating lining and surrounding the tube is placed a packing 6 of granular calcium carbid or other car/bid. Dry calcium oxid may be mixed with the calcium carbid, if desired. A layer of paper may be employed to separate the lime irom the calcium carbid.

End pieces 'Z and 8 are placed at each end of the casing and serve to retain the of lime or asbestos and the packing in place. The nut 2 is shown as secured to the outer -side of the end plate?, which is apertured centrally to receive the tube l. The other end plate 8 is also provided with. a central aperture; but this aperture is made large enough to receive the -nut 3, which isfslidingly fitted therein, The end plates 2' and 8 are preferably made of sheet-iron, so as to have substantially the saine ratio of expansion as the nuts 2 and 3 and. the pipe l. rlhe longitudinal expansion of the pipe l takes place without any injurious effect upon the casing by reason of the sliding connections between the nut 3 and the end plate 8. Suitable terminals 9 and l0 are clamped. onto the ends of the rod l. These terminals should be flexibly connected to some source ofelectric current.

The article which it is desired to heat having beenplaced in the hollow tube current is passed through the tube between the terminals 9 and 1U. This heats the tube and any article which may be placed therein. The degree of heat attained is dependent upon the amount of-curr'ent used and the resistanceof the tube.

The casing l may well be made oi sewer or drain pipe, as shown.

alternating currents are employed to heat easing is objectionable.

Though a section of tubing forms a desiri able heating-chamber, other forms are ini eluded within Y the spirit of my invention. By the use of the term I iron in the specifi cation and claims l intend to cover generic- 5 ally the various forms of iron and steel. In place of using iron or steel tubing it `may sometimes be desirable to use tubes formed out of other metals packed in the material described. For instance, nickel may sometimes be employed as a substance out of lWhich to make the tube, as by using it the temperature at which such a furnace can be Worked will. be increased somewhat.

l/lhile l have illustrated and described the best form of my invention which is new known to me, l do not consider my invention in its broader as eets to be limited to the details shown an described, as they do not form essential features of'my invention.

vJi/'hat l claim as new, and desire to secure by Letters latent of the `United States, is-.

l. in furnace, an iron heating member and e heat-insulating iacking therefor, containing calcium carbii in granular form.

2. ln a furnace, an iron heating-chamber, means for introducing material to be heated Within said chamber, means for connecting said chamber to a source of current and a packing surroundiiig said chamber and containing a carbid.

ln a furnace, an iron heating-chamber` means for introducing material to be heateu Withi, said chamber, means for heating said chamber and a packing surrounding said chamber a'hd in contact therewith, said packing containing calcium carbid.

d. ln n furnace, an iron tube, means for heating said tube, means for introducing material to be heated within said tube, a casing surrounding said tube and a packing between said tube and casing containing calcium carbid in granular form.

5. An electrical furnace, consisting of an iron tube, and a tubular casing surrounding said tube haring end pieces centrallyY apertured to receite said tube, said tube being secured against longitudinal movement with respect to one of saiiLend iieces and free to move in either direction tln'ough the. other end piece.

o. ln a furnace, an iron heatiiig-chan'ibcr, means for hea ting said chamber, means for introducii'ig material to be heated within said i elianiher and a beabinsulating packing suri roui'ifling said iron chamber and in contact g therewith, said packing containing a carbid. l

7. In a furnace, an iron heatingchan1l er, 6o

means for introducingr material to be heated within said chamber, means for connecting said chamber to the source of current and a packing surrounding said chamber and con,- taining calcium carbid in granular form.

8. ln a furnace, an iron heating-chamber, means for introducing material to be heated Within said chamber, means for heating said chamber, and a granular packing surroundihg said chamber containing a substance Which When heated by said chamber may decompose to form a reducing-gas in the interstices of said packing.

9. In a furnace, an iron heating tube, means for connecting said tube to a source of current and a granular packing surrounding said tube, said packing containing a substance which when heated by said tube may reduce to a refractory oxid and a non-oxidizing l 10. In a furnace, a metallic heating-charm ber, means for introducing material to be heated Within said chamber, means for 'connceting said chamber to a source of current to heat the-same and a granular packing surrounding said chamber containing a carbid which when heated by said tube may form a reducing-gas in the interstices of said granular packing and a refractory oxid inert io said metallic heating-chamber.

1]. ln a furnace, ahollow heating member, means for introducing material to be heated Within said hollow member, means for heating said member, and a heat-insulating packing surrounding said member and in contact therewith, said packing containing a carbid.

l2. In a furnace, an oxidizable healing member, means for passing current through said member to heat the same, means for introducing material to be heated within said member, and a heat-insulating packing e'onytaining calcium carbid surrounding said member to protect it from oxidation.

13. In a furnace, an oxidizable heatingchamber, means for connecting said chamber to a source of current, means for introducing material to be heated within said chamber, and a heat-resisting packing surrounding said chamber to protect it from the atmosphere, said packing containing calcium carbid izi granular formr ln witness whereof l have hereunto set my hand this 27th day of October, 1902.

ICRLANI) Zllili.

\l"itnesses:

BENJAMIN l. Ilma.. llnLnN Onronn.

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